This invention relates to an engine valve control apparatus which is mainly for use in an internal combustion engine of a vehicle, and in which at least one of an intake valve or an exhaust valve, both of which are operated by a cam and a return spring, is provided with an electromagnetic actuator which operates the valve in accordance with the state of operation of the engine.
A conventional valve control apparatus is known, for example, as disclosed in Japanese Utility Model Laid-Open No. 52111/1984 wherein the intake and exhaust valves are opened and closed by a cam and a return spring actuated by an electromagnetic actuator in accordance with the operating condition of an engine, to adjust the timing thereof to thereby obtain improved charging efficiency or predetermined combustion characteristics, such as: the desired output characteristics, fuel consumption, and exhaust gas characteristics.
However, the attraction force of an electromagnetic actuator, by virtue of its electromagnetic solenoid, decreases in proportion to the square of the distance between the electromagnetic solenoid and a magnetic pole member which is attracted by the electromagnetic solenoid. Therefore, in order to assure the attraction force required to open and/or close the intake or exhaust valve, the lift or extent of movement of each valve must be made small. This, however, causes problems in attempting to obtain predetermined combustion characteristics. Therefore, in the foregoing prior art control apparatus, it was necessary to increase the attraction force to provide a greater magnitude of lift, which required the use of an electromagnetic solenoid and power source of greater capacity. This resulted in disadvantageous and undesirable increases in the amount of space required and costs associated with the apparatus. These problems are avoided by the present invention.